Lipocalins are small secreted proteins that are believed to be involved in the transport of small, hydrophobic molecules. The lipocalin family is characterized by the structural motif of a barrel formed by eight, anti-parallel, beta-sheets, which are arranged as two orthogonal sheets. The lipocalin family is diverse at the sequence level.
The most related members of the family share three characteristic conserved sequence motifs. Members of this group include: retinol-binding protein; purpurin; retinoic acid-binding protein; xcex12u-globin; major urinary protein; bilin-binding protein; xcex1-crustacyanin; pregnancy protein 14; xcex2-lactoglobin; neutrophil lipocalin and choroid plexus protein. Outlier lipocalins are classified as such because they have 2 or less sequence motifs conserved and these proteins include: odorant-binding protein, von Ebner""s gland protein, probasin and aphrodisin.
The lipocalins are members of the superfamily known as calycins, all of which are ligand-binding proteins for hydrophobic molecules. Other members of the calycin family are fatty acid-binding proteins (FABPs) and avidins. The members of this super-family share some conformational homology, with little sequence homology (Flower, FEBS Letters 354:7-11, 1994; and Flower, J. Molec. Recognition 8:185-195, 1995).
Von Ebner""s gland protein, is also known as tear lipocalin, tear prealbumin or VEGP. It has been shown to be present in the acini of the prostate (Holzfeind et al., FEBS Letters 395:95-98, 1996), acinar cells of the lacrimal glands and von Ebner""s gland (Holzfeind et al., Exp. Eye Res. 61:495-500, 1995). VEGP may also be present in salvia, nasal secretions and sweat. VEGP co-localizes with lysomsomes in serous acinar cells and is also present on polyribosomes from the ER and the Golgi apparatus.
Similar to other lipocalins, VEGP is a carrier for retinol or other small hydrophobic compounds. VEGP binds retinol in vitro, and is believed to have an antimicrobial function in the eye, partly because it binds long chain fatty acids which inhibit activation of lysozyme (Glasgow, Arch. Clin. Exp. Ophthalmol. 233:513-522, 1995). The protein may also inactivate enveloped viruses, help surface spreading of the lipid film in the eye and/or protein the epithelium.
Another member of the lipocalin family includes epididymal-retinoic acid binding protein (ERBP), which has tertiary structural homology to retinol-binding protein from human serum (Newcomer et al. J. Biol. Chem. 265:12876-12879, 1990). ERBP is believed to play and important role in maturation of the sperm as it passes through the epididymis. ERBP has been shown to bind a broad spectrum of retinoids, including retinol (vitamin A) retinal, retinyl acetate, xcex2-ionone, cis retinoids, xcex2-carotene, cholesterol, terpenoids, xcex2-lonylideneacetate, long-chain esters of retinol and retinoic acid (Flower, Biochem. J. 318:1-14, 1996) in vivo and/or in vitro. The retinoids have been demonstrated to play important roles in cell differentiation and proliferation, as well as vision, reproductive biology, and mucus secretion. For a review of retinoids and their role in disease and maintenance of homeostasis, see, Goodman, D., N. Engl. J. Med. 310:1023-1031, 1984.
These and other aspects of the invention will become evident upon reference to the following detailed description of the invention and attached drawings.
In one aspect of the present invention provides a polynucleotide encoding a lipocalin homolog polypeptide comprising a sequence of amino acids that is at least 80% identical to the amino acid sequence as shown in SEQ ID NO: 2 from residue 1 or 17 to residue 170.
In another embodiment, the present invention provides a polynucleotide encoding a lipocalin homolog polypeptide comprising a sequence of polynucleotides as shown in SEQ ID NO: 1 from nucleotide 7 or 58 to nucleotide 516.
In another embodiment, the present invention provides a polynucleotide comprising a sequence polynucleotides as shown in SEQ ID NO: 5 from polynucleotide 1 or 52 to polynucleotide 510.
In another aspect, the present invention provides an expression vector comprising the following operably linked elements: a transcription promoter; a DNA segment encoding a lipocalin homolog polypeptide comprising a sequence of amino acid residues that is at least 80% identical to the amino acid sequence as shown in SEQ ID NO: 2 from amino acid residue 1 or 17 to residue 170; and a transcription terminator.
In another embodiment, the expression vector comprises a DNA segment, wherein the DNA segment comprises a sequence of polynucleotides as shown in SEQ ID NO: 1 from nucleotide 7 or 58 to nucleotide 516.
In another embodiment, expression vector comprises a DNA segment, wherein the DNA segment comprises a sequence of polynucleotides as shown in SEQ ID NO: 5 from nucleotide 1 or 52 to nucleotide 510.
In another aspect, the present invention provides cultured cell into which has been introduced an expression vector wherein said cell expresses the lipocalin homolog polypeptide encoded by the DNA segment of the expression vector.
In another aspect, the present invention provides a method of producing a-polypeptide comprising: culturing a cell into which has been introduced an expression vector, whereby the cell expresses the lipocalin homolog polypeptide encoded by said DNA segment; and recovering said expressed polypeptide.
In another aspect, the present invention provides an isolated polypeptide comprising a sequence of amino acid residues that is at least 80% identical to the amino acid sequence as shown in SEQ ID NO: 2 from residue 1 or 17 to residue 170.
In another aspect, the present invention provides a pharmaceutical composition comprising a polypeptide comprising a sequence of amino acid residues that is at least 80% identical to the amino acid sequence as shown in SEQ ID NO: 2 from residue 1 or 17 to residue 170, in combination with a pharmaceutically acceptable vehicle.
In another aspect, the present invention provides an antibody that specifically binds to an epitope of a polypeptide comprising a sequence of amino acid residues that is at least 80% identical to the amino acid sequence as shown in SEQ ID NO: 2 from residue 17 to residue 170.
In another aspect, the present invention provides an oligonucleotide probe or primer comprising at least 14 contiguous nucleotides of a polynucleotide of SEQ ID NO: 1 or sequence complementary to SEQ ID NO: 1.
In another aspect, the present invention provides a method for detecting a genetic abnormality in a mammal comprising: obtaining a genetic sample from a mammal; incubating the genetic sample with a polynucleotide comprising at least 14 contiguous nucleotides of SEQ ID NO: 1 or the complement of SEQ ID NO: 1, under conditions wherein said polynucleotide will hybridize to the complementary polynucleotide sequence, produce a first reaction product; and comparing said first reaction product to a control reaction product, wherein a difference between said first reaction product and said control reaction product is indicative of a genetic abnormality in the patient.